Finnish Salmon Soup Lohikeitto

Name: Finnish Salmon Soup Lohikeitto
Ingredients: 3 tablespoons butter; 1 leek (thinly sliced (white and light green parts only)); 1 teaspoon kosher salt; 4 cups fish stock (or vegetable or chicken stock. See notes for how to make a fast fish stock if you'd prefer to do so.); 1 bay leaf; 2 large white (red, or gold potatoes, peeled and halved PLUS); 1 pound white (gold, or red potatoes, scrubbed and cubed); 2 carrots (scrubbed and sliced); 1 ½ pounds salmon (boneless and skinless); 1 cup heavy cream; 1/2 cup fresh dill (finely chopped); 2 tablespoons fresh chives (finely chopped)